1. Field of the Invention
This invention relates to a digital information storage device, and in particular to a storage device utilizing magnetic recording.
2. Description Relative to the Prior Art
Modern data processing and computer systems require memory devices for the storage of both programs and data, the size and capacity of the memory depending upon system organization and application. The simplest system may only incorporate a modest amount of semiconductor memory, while a larger more complex system may use a variety of memory devices to fulfill system requirements for intermediate and mass storage.
Magnetic recording of the information is one of the most widely used techniques in such data storage devices. Floppy disk drives, hard disk drives, and tape recording units employ magnetic recording, and these units are available with a wide variety of operating characteristics and storage capacities. They are currently employed, in one form or another, as storage units in most data processing and computer systems.
In the aforementioned devices, relative motion between a magnetic medium and a magnetic head is an essential requirement in effecting the storage of the information. This requirement arises for two reasons. First, the data occurs as one or more time sequential streams of digital bits, and it is necessary to lay down the recorded bit pattern on the medium in a spatial distribution corresponding to the data bit stream. During recording, as the record head gap moves relative to the medium, a data pattern of magnetization is, thus, impressed on the storage medium in accordance with the input data stream. Second, the majority of playback heads of the prior art are sensitive to the rate of change of flux intercepted by the head winding. That is, the recorded fixed flux patterns stored on the medium must move relative to the playback head gap in order to generate a changing flux and hence an induced signal voltage in the head. Both requirements necessitate movement of the medium relative to the head. In general, in the prior art, electromechanical units are used to provide the required motion. In the floppy disk drive, the hard disk drive, and the tape recording unit, the magnetic medium is moved past the magnetic head by means of an electromechanical transducer, e.g., an electric motor. In another storage device, viz. the helical scan recorder, the medium is moved slowly past a high speed rotating head driven by an electromechanical motor. The use of such motors to provide the relative motion between the head and the medium is a common characteristic of many prior art magnetic storage systems.
Additionally, such magnetic storage systems utilize other electromechanical devices in their operation. Disk drives commonly employ electromechanical actuators to position the magnetic head in relation to the recorded tracks of the disk, and most tape recorders employ actuators to urge the tape against a rotating capstan and thereby provide tape motion relative to a fixed magnetic head. Such electromechanical motors and actuators generally contain precision mechanical components, and are inherently expensive. These devices are called upon to perform many repetitive mechanical operations, and must retain their mechanical precision in spite of the wear caused by application of frictional forces over extended operating periods. They also require considerable expenditure of electrical power for their operation.
The present invention provides a magnetic digital data storage device that does not rely on such electromechanical transducers to provide relative motion between head and tape and is, therefore, not subject to above mentioned difficulties.